1. Field of the Invention
The present invention relates to a method of using a suction type chuck to hold a workpiece and a holding system of the same.
2. Description of the Related Art
As related art, there is the workpiece holding system disclosed in Japanese Patent Publication (A) No. 64-58486. This workpiece holding system is a suction type chuck system provided with a nozzle for circulating pressurized gas, a reduced pressure chamber provided at a suction plate for chucking (holding by suction) a workpiece comprised of a wafer, and a communication passage communicating the reduced pressure chamber and nozzle.
When chucking a wafer, first, the suction plate is placed on the wafer to form a closed reduced pressure chamber. Next, the nozzle is fed pressurized gas to suck out the gas in the communication passage. Due to this, the reduced pressure chamber connected with the communication passage is reduced in pressure and the wafer is given suction and chucked.
Further, when unchucking the wafer, the supply of pressurized gas to the nozzle is stopped and the atmosphere in the reduced pressure chamber is made equal to the atmospheric pressure. Due to this, the suction on the wafer is released and the wafer is unchucked.
However, in the above holding method of the related art, when chucking a workpiece, the suction chamber is arranged to contact the workpiece, then the inside of the suction chamber is reduced in pressure. Further, when unchucking the workpiece, the atmosphere flows in from the nozzle, no longer supplied with pressurized gas, through the communication passage to the inside of the suction chamber, whereby the negative pressure state inside the suction chamber is released.
Therefore, there were the problems that attachment and detachment (chucking and unchucking) of the workpiece required a relatively long time and it was difficult to reduce the attachment/detachment time as strongly demanded.